Over the last two decades there has been a significant increase in the presence of motorized rail transportation in urban areas resulting in an increasing need for methods of reducing the high frequency sounds which result from the twisting of the axle and sudden subsequent release of the twist as a curved rail is negotiated by the wheels of a train.
Initially, lubrication and noise reduction were addressed by pumping oil under pressure through nozzles directed at the wheel contact point with the track. However, these types of lubricant showed the tendency to creep onto the crown of the rail, which caused unacceptable slippage. This technology also left oil on the track and surrounding area. Due to environmental concerns caused by this oil contamination, solid stick lubricants have increased in popularity and have been useful for reducing friction and otherwise varying the frictional characteristics of steel to steel contact between train wheels and railway tracks. Additionally, solid lubricants have improved the accuracy and effectiveness of the delivery of lubricant to the flange. In a typical application, a stick lubricant is applied by a holding means to the wheel flange and/or tread of a train.
Solid lubricants are known in the art and generally comprise a solid lubricant in combination with other components. The type and amount of the components in the solid lubricant stick may vary depending on the characteristics desired, for example increased or decreased friction. Solid lubricant sticks, or composition sticks, are described, for example, in U.S. Pat. Nos. 5,173,204; 5,308,516; and 6,136,757 (which are incorporated herein by reference).
Applicators generally comprise a holding means to retain the lubricant or composition stick in position, and contain a pushing mechanism for maintaining the composition stick in contact with the wheel. Applicators are generally used in system where steel-to steel contact may occur, for example, on the underside of a locomotive or rail car, or along any rail system, for example rails in an elevator shaft, where space is at a premium. Therefore, it is desired that the applicator requires as little space as necessary, may easily be reloaded with new lubricant sticks, and is reliable.
U.S. Pat. No. 4,811,818 (Jamison) describes an applicator in which a lubricant, or composition stick, is held in place by a stud mounted on a bracket. The bracket is biased by a torsion spring such that the stick is in contact with the wheel. However, the lubricant or composition stick in Jamison is exposed to dust, dirt and oil present in the environment of the locomotive underside, which affects its performance. Furthermore, in this system, lubricant or composition stick manufacture is complex, as a stud, or a recessed nut, must be inset into the upper end of the stick for attachment to the applicator. Replacement of the stick therefore is complex.
U.S. Pat. No. 5,054,582 (Aracil) discloses a solid stick applicator having a biased pusher arm, which applies pressure to the stick as the arm progresses through an arcuate path. The pusher arm enters the applicator body through a slit that also functions as a register to align the pusher against the composition stick, and the spring assembly is exposed. This mechanism is easily jammed with contamination and debris during use, is difficult to maintain, and is subject to premature wear.
Another composition stick applicator is taught in U.S. Pat. No. 5,251,724 (Szatkowski et al), in which the applicator has a pair of coiled flat springs (i.e. constant force springs; CFS) that exert a constant forward force on the lubricant or composition stick such that it is urged forward out of the applicator and against a steel surface, for example a wheel flange. Retraction of the spring assembly to the rear allows insertion of a replacement stick through a cutout on the side of the applicator. A similar applicator comprising coiled flat springs is described by in U.S. Pat. No. 5,337,860 (Burke et al.). While the '724 and '860 applicators require less space when replacing the lubricant, the cutout results in significant contamination of the stick and the applicator and jamming may occur. Furthermore, the coiled flat springs tend to fail prematurely, resulting in increased maintenance.
Mitrovich et al. (U.S. 2003 0,101,897) teaches a composition stick applicator having a holder into which a dispensing insert is placed. The dispensing insert includes a slide mechanism onto which is attached a coiled flat constant force spring (CFS). A lubricant or composition stick is placed in the holder, and the dispensing system is inserted into the holder behind the lubricant stick. The stick thus extends the CFS such that the coiled portion of the spring pushes the stick out of the applicator onto the desired surface. While this design permits easy removal and cleaning of the holder to minimize debris build up, during regular use and reloading, the solid stick translates back and forth causing bending stresses within the coiled flat CFS. As noted above with reference to U.S. Pat. Nos. 5,251,724 and 5,337,860, these cyclical stresses cause the CFS to quickly develop fatigue cracks, resulting in short spring life. Frequent spring replacement is required for proper function of the lubrication system.